1. Field of the Invention:
This invention pertains generally to binding materials. More particularly, the present invention relates to a means for the strapping, binding, or bundling of articles.
2. Description of the Prior Art:
Known binding materials include a wide variety of natural and synthetic compositions which are used alone or in combination with each other. These binding materials are used in the form of strings, straps, strips, wires, tapes, tubes, bands, and sheets. The choice of form and/or of material is predicated on the size, dimension and nature of the article to be bound. For example,, binding materials used for bag closure generally are manufactured from strips of formable sheet material, such as paper, thermoplastic high polymers, fabrics or the like and are adhesively bonded in matching relation to form a two-ply band and containing a wire strand. These binding materials or bag closures have gained wide acceptance. Such a binding material made from sheets of polyethylene-imgregnated paper and suitably bonded together is disclosed and described in U.S. Pat. No. 3,068,135. Binding materials having a thermoplastic poylmer, such as polyvinyl chloride covering a wire strand are shown and disclosed in U.S. Pat. Nos. 2,767,113 and 3,409,194. The binding materials of the type described in the aforementioned patents receive their strength exclusively from the inserted wires. The paper and thermoplastic covering surrounding the wires serve only to improve handling and prevent damage to the wall of the bag or the bundled fragile articles, such as plant stems, etc. by the wire. However, this type of binding material has a glaring detect in that the wire strand breaks frequently at the bending point and most often upon a twisting operation. Such breaking of the wire results in the complete failure of the binding material since the paper or the extruded plastic covering does not have the mechanical strength to hold together the bundled article or bag. Therefore, a need exists for a high strength covering for wire strands used as binding materials which would have sufficient mechanical strength to maintain binding ability despite failure of the wire strand.
Additionally, binding materials made of thermoplastic high polymers such as polyethylene, polystyrene, polypropylene, and nylon, have also been used as tapes or bands for unitizing packages. These are generally used without reinforcing elements or stiffening elements such as wire strands. The manufacture of the conventional package tapes generally is performed by extruding and, thus, is highly oriented by longitudinally stretching the film. However, these too possess certain disadvantages. For instance, the prior art non-metallic tapes or bands often produce objectionable tears or splits and have a tendency to fibrilate with the resultant loss of mechanical strength properties. Therefore, the need also exists to improve the properties of binding materials to provide a high tensile strength, and high resistance to transversal tear along with providing a low resistance to longitudinal tear while maintaining the cohesion of the film adjacent to the tear.